Efficacy Evaluation And Dose Comparison Of Helical Tomotherapy And IMRT For Pediatric Medulloblastoma

Background and purposeMedulloblastoma(MB)is one of the malignant neoplasms of children's central system,Accounting for 25?30%of pediatric brain tumors in children?The tumor grows rapidly and is easy to encroach on the brain stem.It is difficult to remove the tumor completely when it encroach on the brain stem.Moreover,Medulloblastoma can be disseminated through cerebrospinal fluid.MB is sensitive to radiotherapy,but surgical resection is still the main treatment for MB.At present,individualized adjuvant therapy for children with different Medulloblastoma is still controversial.It is generally accepted that the best treatment method is surgery combined with postoperative chemoradiotherapy.However,due to the high degree of malignancy and rapid progression of the tumor,it is difficult to remove the tumor when it infringes the brainstem,and the prognosis of the child is poor when it spreads along with the cerebrospinal fluid.Therefore,whole brain and whole spinal cord radiotherapy has become an important adjuvant therapy for medulloblastoma in children.Since the target area of whole-brain and whole-spinal cord radiotherapy is longer and there are more organs at risk around the target area,conformal radiotherapy and helical tomography radiotherapy also appear to be very important in the treatment of Medulloblastoma.More and more studies show that helical tomography has greater advantages in the homogeneity index and coverage index of the target area than Intensity modulated radiation therapy.Conformal Intensity modulated radiation therapy(IMRT)makes high uniform target dose distribution in the area by dose optimization and reverse operation.But IMRT maximum beam width were usually less than 40 cm,for the whole brain full of the spinal cord long a target need to take block light,easy to cause the target area appear cold spots cohesion.Helical TOMO therapy(TOMO)Tomotheraphy(TOMO)use 6MV medical linear accelerator to replace the ordinary CT X-ray tube,with spiral CT scanning to achieve the continuous rotation of the frame and the movement of the bed.TOMO can combine intensity modulated radiotherapy,image guided radiotherapy,and dose guided radiotherapy.In medical imaging,2.8mv X-ray was used for medical imaging.Under the guidance of mev medical imaging,the 3D image of the target area reconstructed by MVCT was compared with the image of positioning CT.After correcting the positioning error in 3D,6MV high-energy X-ray was used for conformal intensity modulated radiotherapy.It can greatly improve the conformation degree of the target area,improve the uniformity of the dose distribution in the target area,reduce the exposed dose of organs at risk,so as to protect the organs at risk around the target area and reduce the occurrence of toxic and side effects of radiotherapy.TOMO irradiation range can reach 40cm×160cm,which can effectively solve the connection problem of long target area and avoid the cold hot spot problem of irradiation dose within the target area of long target area.In this studv.the dosimetric differences between TOMO and IMRT in the treatment of children's medulloblastoma were compared to analyze and discuss the efficacy and safety of TOMO and IMRT in the treatment of children's medulloblastoma,to provide evidence-based medical evidence for clinical application.Part ? dosimetric comparison of TOMO and IMRT after operation for children medulloblastomaObjective:To compare the difference of dose distribution between Helical TOMO(TOMO)therapy and Conformal Intensity modulated radiation therapy(IMRT)of children's Medulloblastoma.Methods:A total of 10 children with medulloblastoma admitted to the first affiliated hospital of zhengzhou university from 2017 to 2019 were collected,including 6 males and 4 females.All children received whole brain and spinal cord radiotherapy one month after surgery.Average height 117cm.Two different radiotherapy plans IMRT and TOMO were designed for all 10 children.Comparing two radiotherapy target OuDeShi morphic index(coverage index,CI),uniformity index(homogeneity index,HI)and crisis organ(OAR)dose of illuminated.Result:Compare conformant index(CI),homogeneity index(HI),and the dose to organs(OAR)between TOMO and IMRT.The results showed that the TOMO plan HI was 1.049±0.01 better than the IMRT group 1.15±0.02(P<0.05),and the TOMO plan CI was 0.864±0.02 better than the IMRT group 0.816±0.05(P<0.05).Dmax point of bilateral optic nerve;Dmean of eyesball;The volume percentage of organs at risk contained in 5Gg and 10Gy in the heart V5 and V10 and Dmax point of heart;20Gy contains the volume percentage of the organ at risk V20(%)of lung;mean dose and maximum dose of lung;The volume percentage of the organ at risk contained in stomach 5Gy was V5(%);The Dmax point of small intestine maximum exposure dose were lower than that of IMRT group.Preliminary results showed that the target area conformal index(CI)of the TOMO group was better than that of IMRT,and the difference was statistically significant(P<0.05).The uniformity index(HI)of TOMO plan was better than that of IMRT group,and the difference was statistically significant(P<0.05).The uniformity of radiotherapy dose of TOMO group was better than that of IMRT group.The average exposed dose,maximum exposed dose and high coverage area wrapping volume of some organs at risk were all lower than those of the IMRT group,indicating that the spiral tomography radiotherapy for medulloblastoma can reduce the exposed dose of organs at risk to a certain extent,possibly reducing the incidence of side effects and the probability of secondary tumor occurrence.Conclusion:Both IMRT and TOMO can meet the prescribed dose requirements for childhood medulloblastoma.However,the target coverage index and dose homogeneity index of TOMO were better than that of IMRT.Moreover,TOMO can reduce the exposure of organs at risk without affecting the quality of the target area.At the same time,the probability of adverse reactions is reduced and the quality of life of patients is improved.Part ? efficacy and safety of TOMO and IMRT in the treatment of childhood medulloblastomaObjective:Summarize the efficacy and safety of TOMO and IMRT in the treatment of medulloblastoma in children by receiving helical tomography radiotherapy.In order to provide strong evidence of evidence-based medicine for clinical application.Methods:A retrospective analysis was conducted on children diagnosed with medulloblastoma by postoperative pathology in the first affiliated hospital of zhengzhou university from 2014 to 2019,including 50 cases in each of the TOMO group and IMRT group.All 50 patients received surgery and postoperative helical tomography radiotherapy at a dose of 30.6-40gy for the whole brain.The dose was 1.8gy × 17-2.0gy ×20 times,and was added to the posterior fossa to 50.4gy-60 Gy.The dose was 1.8gy ×30 times-2.0 times 30 times.The total spinal cord dose of 30.6 gy-36 Gy was 1.8 Gy×17 times-2.0 Gy×17 times.All radiotherapy plans are prepared by highly qualified physicists according to the prescribed dose required by the radiotherapy clinician of our hospital and the limits required for organs at risk.All patients were reviewed monthly for whole-brain and spinal MRI,tumor markers,liver and kidney function,and blood routine.Some patients received concurrent chemoradiotherapy with EP regimen(cisplatin+etoposide).The objective response rate(ORR),disease control rate(DCR),progression free survival(PFS),overall survival(OS)and adverse reaction rate of TOMO in treating medulloblastoma were evaluated according to the outcome indexes of imaging diagnosis and test diagnosis.Result:Among the 50 children treated with IMRT,41 patients with complete response(CR),7 patients with partial response PR,1 patient with stable disease SD and 1 patient with progressive disease PD.Response rate(RR)=CR+PR=98%disease control rate(DCR)=CR+PR+SD=96%.Among the 50 children treated with IMRT,39 cases of CR,7 cases of PR,2 cases of SD and 2 cases of PD were achieved aftertreatment.The effective RR was 96%;The disease control rate DCR was 92%.The main adverse reactions were blood adverse reactions,digestive system adverse reactions,fatigue and headache.Grade 1-3 was the main level of blood adverse reactions,and grade 4 was rare.The adverse reactions of digestive system were mainly of grade 1?2,but no grade 4 adverse reactions were found.Conclusion:For children's medulloblastoma,the efficacy of helical tomography radiotherapy was similar to that of conformation intensity modulated radiotherapy,and the short-term effective rate and disease control rate of the two groups were similar.Moreover,there was no significant difference in the incidence of blood adverse reactions and gastrointestinal adverse reactions between the TOMO group and the IMRT group.